Caracterização de produtos comerciais e da fermentação on farm para o controle de Pratylenchus brachyurus em soja

Abstract

The management of soybean root lesion nematode (Pratylenchus brachyurus) is based on the integration of cultural, chemical, and biological factors, with cultural practices and biological control considered essential tools. The first part of this study presents a literature review focusing on the pathosystem P. brachyurus-soybean, as well as the main management practices. Additionally, biocontrol agents are discussed, with emphasis on the Bacillus genus and the potential benefits of adopting this biological control agent within the integrated nematode management in the field. In the second part of the study, the quality of on-farm fermented products in different regions of Mato Grosso State was evaluated during the 2nd crop of 2019/20 and the 2020/21 crop, with a total of 125 collected samples. These samples were used to quantify endospore-forming bacterial cells and assess the performance of these fermentates in reducing P. brachyurus penetration in soybean roots. Microbiota analysis was conducted between samples of two commercial products, Onix and Nemacontrol, and their fermentations obtained from different production systems. Metataxonomic sequencing of the samples utilized a partial fragment of the 16S rDNA region. Alpha diversity and beta-diversity of the microbial samples were assessed. Subsequently, the fermentation conditions and field efficiency were validated in five trials conducted with producers in areas with a history of losses due to root lesion nematodes. Concerning endospore-forming cells, only 3 products maintained an average quantification of 108 CFU mL-1, both in the commercial product and in the fermentate, with all of them having Bacillus amyloliquefaciens as the base. Among the variables analyzed for the efficiency test, only nematode penetration in the roots showed a difference between the samples, with 4 distinct products standing out. It was observed that the use of on-farm fermented products under optimized conditions may allow for nematode reduction. Microbial analysis revealed a relative abundance of 100% in commercial samples, while the fermented samples showed a wide variation in the composition of different bacteria genera, with no discernible pattern among them. Alpha diversity showed separation between the composition of commercial and on-farm products, while beta diversity showed clustering among the fermented and commercial samples. Understanding the composition and efficiency of the fermentation system is essential, with on-farm fermentation being a tool to increase productivity. Areas should be managed with a focus on integrating biological control with other management practices.